In my opinion, there are enough SQL-oriented forums here: one for newbies, SQL and PL/SQL experts, plus homework one. I believe a puzzle is yet another (tricky, though) (PL/)SQL problem which might also fit into General or even Community hangout forums. There are not that many of them (puzzles, I mean) and I think that we don't need a new forum for such questions.

The purpose of a puzzle forum will be completly different from the homework or SQL-PL/SQL newbie in that it is not for newbie.
It is different from SQL (or PL/SQL) expert in that it is not for real world problem.
I think we will can find more than the 50 topics Collaboration Suite forum has.
In addition to fun, a puzzle forum may be the place to show some exotic and/or high level features, describe in details tricks and so on.
The "connect by level" as well as its "group by cube" predecessor generator trick were found to solve a puzzle (generating row without using an existing table/view) and was/is used everywhere now.

And even I think, 'Puzzles' may not exactly fit to the general and Community hangout forums as it has its own seriousness ( though its primarily for fun ). It is true that there are not many of them right now . But once , it is started it can attract lots of members with high level skills .

I've started some puzzles in General forum.
I suggest to add and indicator of complexity in the title.

Here's a starting point:
* = requires knowledge and experience in SQL or PL/SQL but not expert one, or is a known problem, can be solved in less than an hour by an expert
** = requires expert skills, combines several techniques like analytic functions, hierarchy query, aggregate... can be solved in a couple of hours to one day by an expert
*** = requires high level, complex or little known features (model, xquery, 11g, 12f... new features...), may require several days of work to be solved by an expert.

Just an idea: we could create a sticky in the General forum which would be some kind of the puzzle's menu. In there, we'd put links to all puzzle topics with a short description so that anyone could easily find it.

But i am slightly conern on why less response to Puzzle section curretly .( Less views ; Less replies )

Maybe it is not so popular among the community. Maybe it is just popular among those who are interested in it.
Maybe the first puzzles are too difficult. Please post your owns.
Maybe people prefer posting their problems rather than answering to puzzles.